The invention is directed to a condensate colorimetric nitrogen analyzer oxide that determines the content of nitrogen oxides in exhaled breath condensate.
Conventional assessment of severity of airway diseases, including asthma, consists of measures of pulmonary mechanics which are effort dependent and thus not suitable for many pediatric patients, mechanically ventilated patients, or patients with neuromuscular disease. See Crapo R., Pulmonary-function testing. N. Engl. J. Med., 331; 1:25-30; 1994; and American Thoracic Society/European Respiratory Society: Respiratory mechanics in infantsxe2x80x94physiologic evaluation in health and disease, Am. Rev. Respir. Dis., 1993; 147:474-96. Currently the Peak Expiratory flow meter is the only method commonly available for home use by asthmatics to monitor the state of their airway disease. This test suffers from being an insensitive indicator of airway inflammation, and is effort dependent. Other physiologic parameters require expensive machines and experienced operators to obtain reproducible results. Klein R., Fritz G. Yeung A., McQuade E., Mansell A., Spirometric Patterns in Childhood Asthma: Peak Flow Compared with Other Indices. Pediatr. Pulmonol., 1995, 20:372-379.
Endogenous production of nitrogen oxide in the human airway has been shown to be increased in patients with asthma and other inflammatory lung diseases. Gaston B., Drazen J., Chee, C., et al. Expired nitric oxide concentrations are elevated in patients with reactive airways disease. Endothelium. 1993; 1:S87; Gustafsson, I. E., Leone A. M., Persson M. G., Wiklund N. P., Moncada S., Endogenous nitric oxide is present in the exhaled air of rabbits, guinea pigs and humans. 1991; 181; 2:852-857. However, measurement of gas phase nitric oxide (nitrogen monoxide) per se in the parts per billion range found in the airway requires the use of mass spectrometry or chemiluminescent technology, which are cumbersome, expensive and not reasonably suited for home use.
Moreover, measurement of aqueous phase higher oxides of nitrogen compounds such as S-nitrosothiols, nitrite and nitrate, which are not nitrogen monoxide but which are likewise elevated in concentrations in subjects with inflammatory lung disease, has required that patients be hospitalized for invasive airway sampling procedures, including airway intubation and bronchoalveolar lavage. Gaston, B., Reilly J., Drazen J., et al., Endogenous nitrogen oxides and bronchodilator S-nitrosothiols in human airways. Proc. Natl. Acad. Sci., 1993; 90:10957-10961.
The invention provides a device for determination of the content of higher oxides of nitrogen in exhaled breath condensate which comprises a conduit having an exhalate condensing portion with an inlet and an outlet (the inlet can be configured to fit with a mechanical respirator or, for direct use by the patient, an inlet assembly providing one-way ingress of ambient atmosphere to the device can be associated with the inlet of the conduit exhalate condensing portion); a coolant jacket coaxially surrounding said exhalate condensing portion; a gas release port; and, in enclosed fluid communication with said conduit exhalate condensing portion outlet, a sample assay assembly comprising (i) an optical analysis chamber, for example, clear or translucent, attached to the outlet to receive condensate fluid and having a reagent entry port (ii) a reagent chamber in enclosed fluid communication with the reagent entry port and (iii) a pliable element connecting the outlet and the analysis chamber and forming a portion of the reagent chamber such that flexion of the pliable element closes communication between the outlet and the analysis chamber and contracts the reagent chamber so as to deliver to the analysis chamber controlled amounts of condensate and reagent. The device is disposable and inexpensive, and is used to collect human exhalate for colorimetric assay of liquid and gas phase nitrogen oxides to assist in evaluation of airway inflammation.
In a preferred embodiment the device further comprises an inlet assembly providing one-way ingress of ambient atmosphere to the exhalate condensing conduit inlet. This is ideal for the patient who is breathing directly into the device, rather than the situation where the device is connected to a mechanical respirator.
In a preferred embodiment the device further comprises, between the inlet assembly and the exhalate condensing conduit portion, a filter capable of removing particulate matter from exhaled air which passes therethrough.
In another preferred embodiment, the device further comprises a coolant material in the coolant jacket.
In another preferred embodiment, the device further comprises a reagent composition capable of detecting a nitrite or nitrate in an exhalation condensate sample.
In another preferred embodiment, the device further comprises a reagent-permeable membrane in the reagent entry port.
In another preferred embodiment, the device further comprises a rupturable membrane in the reagent entry port.
In another preferred embodiment, the inlet assembly further includes therein a filter capable of removing ambient nitrogen oxides from exhalate passing therethrough.
In another preferred embodiment the exhalate condensing conduit portion comprises a single lumen conduit having a lumen diameter sufficient to cause substantially no resistance to the flow of exhalate therethrough.
In another preferred embodiment the exhalate condensing conduit portion comprises a plurality of conduit tubules having a collective lumen diameter sufficient to cause substantially no resistance to the flow of exhalate therethrough.
The purpose of this invention is to condense exhaled lung gas and vapor for aqueous phase nitrogen oxide analyses. This will assist in the evaluation of the human airways"" production of nitrogen oxides in both gas and several liquid phase states, including nitrite and nitrate, with potential for multiple other studies to help delineate the lung""s redox environment and the airways"" degree of inflammation. The investigations which have resulted in the present invention indicate that easily measured liquid phase exhaled nitrogen oxides, nitrite and nitrate, are likewise elevated in asthmatic subjects during periods of inflammation (see abstract enclosed, unpublished data). Utility in the clinical setting for inexpensive and domiciliary evaluation of airway inflammation in various disease states, including asthma, is the primary purpose of the device of the present invention and its utility has been proven, inter alia, as demonstrated herein.
The invention is comprised of cold tolerant materials and consists of two tubing units, one inside the other. Surrounding the inner tube or set of tubes, and contained by the outer tube, is a chemical substance which has a high specific heat, and therefore, once frozen, can maintain freezing temperatures for an extended period of time. The disposable unit can be frozen in a standard size home freezer and then connected together with collection and analysis instruments as a compact integral unit.
Attached to the proximal portion of the unit is a port through which the subject breathes. This consists of two one-way valves which direct atmospheric air or selected gases to the patient""s lungs during inspiration, and channel exhaled gas down a condensing tube. Gas moves in only one direction through the condensing apparatus. Inserted between the breathing port""s mouthpiece and the condensing chamber is a microporous filter which traps all small particles (such as saliva or sputum), is impermeable to liquids, but allows gas and vaporized fluids of less than 0.3 microns in diameter to pass. This acts as a saliva trap and may also act as a filter for the larger fluid particles which may be aerosolized in the larger airways.
The distal end of the condensing chamber tube(s) is attached to a collecting apparatus which utilizes gravity to trap condensed fluid. At the bottom of this trap is a clear plastic analyzing chamber in which the sample is sequentially warmed, sealed, reacted with colorimetric reagents and analyzed spectrophotometrically by the non-disposable colorimeter.
The patient breathes comfortably in and out through the mouthpiece. Lung fluid vapor collects on the inner surface of the inner tube(s) of the condensing apparatus starting immediately. Gravity carries the larger droplets down the tube, these droplets recruiting other small droplets on their trip to the collecting vial distally. Alternatively, after a fixed period of tidal breathing, the condensed fluid can be expressed down the inner tube with a device similar to a syringe plunger. Aqueous phase nitrite and nitrate can be measured by standard colorimetric assays, and can be reasonably quantified by simple tests performed by patients in their homes.